As the modern demands in living environment, the lighting is playing an even more important role than ever. Nowadays, the lights are no longer for illuminations for people to see in the dark, lights are also used in creating certain atmosphere and are becoming part of an architecture or art design. However, as the energy resource is becoming scarce, the energy consumption also becomes an important concern when using lights. The recent development of LED has brought about the revolutionary changes in the lighting devices. The LED lighting devices can be directly controlled by a computer program for changing the color, the intensity and the ON/OFF interval to display full color ranges. This is more visually appealing than the conventional neon-light devices. An additional benefit of using LED lighting devices is that the energy consumption is lower than the conventional neon-light devices.
As many LED lighting devices are used outdoors, such as sport venues or the outer wall of a building, it is imperative that the device is water-proof. FIG. 1 shows a schematic view of the partial structure of a conventional LED light device, including a light shade 11, a circuit board 12 with a plurality of LEDs 13, and a base holder 14. Light shade 11 is engaged to the top of base holder 14, and the connecting part is sealed with water-proof glue. Both sides of light shade 11 and base holder 14 include a top side cover 15 and a bottom side cover 16 that the interior space is completely sealed to prevent the water from coming in. However, this type of structure has the following drawbacks:    1. The water resistance is poor in an environment where the temperature experiences significant changes. Because this type of lighting device is usually longer than 1 meter, and mainly comprises a light shade, a circuit board and a base holder, all of them made of different materials. Therefore, the thermal expansion coefficients of these three major components may be very different from one another. For example, a base holder is usually made of aluminum, and the light shade may be made of acrylic. In an environment where the summer temperature can reach as high as 30-40° C., and the winter can be as cold as −5-20° C., the deformation of these components can be very different due to different thermal expansion coefficients, such as expansion or shrinkage. As a result, the tight seal between the light shade and the base holder can be broken and leads to water leakage.    2. The manufacturing process is complicated and time-consuming. In addition to installing the circuit board to the base board and connecting the LEDs, the water-proof glue must be applied to the connection between the base holder and the light shade, which may be longer than 1 meter. As a result, the yield rate is poor if additional caution is not taken during the sealing process.